Six military police officers were killed and eight other soldiers wounded in two attacks in southern Iraq yesterday in the biggest setback to British forces since the war was declared officially over.

The bodies of the dead - the largest number of British military personnel to be killed by hostile fire since the war began and the first to die since April 6 - were recovered from the town of Majar al-Kabir, 15 miles south of Amara.

In an emergency statement last night the defence secretary, Geoff Hoon, told the Commons that the dead soldiers had been engaged in training the local Iraqi police.

He said local information suggested they might have been involved in what he described as "an incident" at the police station.

"I regret that at this stage I am unable to provide any further details. British commanders are obviously investigating the situation as a matter of urgency," Mr Hoon said.

In a separate incident at 7.30am troops from the 1st Battalion Parachute Regiment engaged in a routine patrol in the same town were ambushed by guerrilla forces.

Their two vehicles were attacked with rocket-propelled grenades, heavy machineguns and rifle fire from "a large number of Iraqi gunmen", the defence secretary told MPs.

The paratroopers returned fire and called for assistance. When a troop of Scimitar vehicles and an RAF Chinook helicopter arrived nearby they also came under fire.

Mr Hoon said eight British troops had been injured - one on the ground and seven in the helicopter - and were taken to 202 Field Hospital. Two have since been transferred to a US field hospital in Kuwait for "specialist treatment for very serious injuries".

Mr Hoon, who said an investigation was under way into whether the two attacks were connected, cautioned against reaching wider conclusions about the security situation in southern Iraq, and promised coalition forces "will not be deflected from their efforts by the enemies of peace".

But British commanders began a review of their peacekeeping tactics in the face of what one military source described as attacks from "pretty organised opposition".

It was unclear last night whether the soldiers were attacked by a hardline Shia group or by disaffected former Iraqi troops, although some analysts immediately blamed the attack on Sunni Muslims still loyal to Saddam Hussein, who have been striking US targets in the north and west.

They may have decided to extend their operations southwards, especially knowing that the British soldiers, having shed their body armour, offered a soft target.

General Richard Myers, the chairman of the joint chiefs of staff, said the attacks on British forces and recent strikes on US soldiers could be part of a coordinated resistance. "We know that there are Ba'ath members that don't want this country to go to a democratic government," he said.

"They are still out there, there are other paramilitaries probably that have joined them. How organised is yet to be determined. That's one of the things we've got intelligence looking at," he added.

Lieutenant-Colonel Ronnie McCourt, a British army spokesman in Basra, said the British troops patrolled the region, close to the Iranian border, regularly and that yesterday's events in no way reflected the general security situation in the south-east.

"It's normally very quiet down here," he said. "We've been here nearly two months now and this is the first time people have been deliberately, consciously shooting at us."

But with Pentagon officials warning of a ratcheting-up of attacks against coalition forces there were fears the Amara incidents could mark the start of an escalation of violence against British troops.

While 18 US soldiers have been killed by enemy fire in Iraq since George Bush declared major combat over on May 1, yesterday's events mark the first British fatalities since April 6, bringing the number of British personnel killed since the start of the conflict to 43.

Defence sources said the attacks would be met with what they called a "robust response". However, military commanders said they hoped the attacks were isolated.

They made it clear that they wanted to maintain their low- key tactics in the battle for hearts and minds - tactics on which they pride themselves and which contrast with those of their US counterparts.

There are about 12,000 British troops in southern Iraq. Ministry of Defence sources said there were no plans to increase that number. Some of yesterday's casualties were due home at the end of June.

Tony Blair's official spokesman said the prime minister heard the news of the casualties with sadness. "It goes without saying that he believes those who died have died with honour doing a very worthwhile job, serving their country with great distinction."

The tragedy is certain to increase pressure on No 10 at a time when Mr Blair is in trouble with his own supporters over the coalition's failure to find weapons of mass destruction.

Urging the MoD to send more troops if necessary, the Tory defence spokesman, Bernard Jenkin, noted: "It is still too early to tell if this signals a general worsening of security in Iraq."

The Russian president, Vladimir Putin, on a state visit to Britain, offered his country's sympathy. He said: "Our sincerest condolences for the loss of the British soldiers in Iraq.

"It is clear for everyone that in spite of the differences that existed before today we need to act urgently."

· The Pentagon last night said it was aware of, but could not confirm, reports that Saddam Hussein's information minister, "Comical Ali", had been arrested by US troops in Baghdad. Relatives reportedly said that Mohammed Saeed al-Sahaf had been hiding in a family house and was caught at a US roadblock. Al-Sahaf gained notoriety during the war by his denials Iraq was losing.